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 // © 2016 and later: Unicode, Inc. and others.
 // License & terms of use: http://www.unicode.org/copyright.html
 /*
 *******************************************************************************
 *
 *   Copyright (C) 1999-2011, International Business Machines
 *   Corporation and others.  All Rights Reserved.
 *
 *******************************************************************************
 *   file name:  utf.h
 *   encoding:   UTF-8
 *   tab size:   8 (not used)
 *   indentation:4
 *
 *   created on: 1999sep09
 *   created by: Markus W. Scherer
 */
 
 /**
  * \file
  * \brief C API: Code point macros
  *
  * This file defines macros for checking whether a code point is
  * a surrogate or a non-character etc.
  *
  * If U_NO_DEFAULT_INCLUDE_UTF_HEADERS is 0 then utf.h is included by utypes.h
  * and itself includes utf8.h and utf16.h after some
  * common definitions.
  * If U_NO_DEFAULT_INCLUDE_UTF_HEADERS is 1 then each of these headers must be
  * included explicitly if their definitions are used.
  *
  * utf8.h and utf16.h define macros for efficiently getting code points
  * in and out of UTF-8/16 strings.
  * utf16.h macros have "U16_" prefixes.
  * utf8.h defines similar macros with "U8_" prefixes for UTF-8 string handling.
  *
  * ICU mostly processes 16-bit Unicode strings.
  * Most of the time, such strings are well-formed UTF-16.
  * Single, unpaired surrogates must be handled as well, and are treated in ICU
  * like regular code points where possible.
  * (Pairs of surrogate code points are indistinguishable from supplementary
  * code points encoded as pairs of supplementary code units.)
  *
  * In fact, almost all Unicode code points in normal text (>99%)
  * are on the BMP (<=U+ffff) and even <=U+d7ff.
  * ICU functions handle supplementary code points (U+10000..U+10ffff)
  * but are optimized for the much more frequently occurring BMP code points.
  *
  * umachine.h defines UChar to be an unsigned 16-bit integer.
  * Since ICU 59, ICU uses char16_t in C++, UChar only in C,
  * and defines UChar=char16_t by default. See the UChar API docs for details.
  *
  * UChar32 is defined to be a signed 32-bit integer (int32_t), large enough for a 21-bit
  * Unicode code point (Unicode scalar value, 0..0x10ffff) and U_SENTINEL (-1).
  * Before ICU 2.4, the definition of UChar32 was similarly platform-dependent as
  * the definition of UChar. For details see the documentation for UChar32 itself.
  *
  * utf.h defines a small number of C macros for single Unicode code points.
  * These are simple checks for surrogates and non-characters.
  * For actual Unicode character properties see uchar.h.
  *
  * By default, string operations must be done with error checking in case
  * a string is not well-formed UTF-16 or UTF-8.
  *
  * The U16_ macros detect if a surrogate code unit is unpaired
  * (lead unit without trail unit or vice versa) and just return the unit itself
  * as the code point.
  *
  * The U8_ macros detect illegal byte sequences and return a negative value.
  * Starting with ICU 60, the observable length of a single illegal byte sequence
  * skipped by one of these macros follows the Unicode 6+ recommendation
  * which is consistent with the W3C Encoding Standard.
  *
  * There are ..._OR_FFFD versions of both U16_ and U8_ macros
  * that return U+FFFD for illegal code unit sequences.
  *
  * The regular "safe" macros require that the initial, passed-in string index
  * is within bounds. They only check the index when they read more than one
  * code unit. This is usually done with code similar to the following loop:
  * <pre>while(i<length) {
  *   U16_NEXT(s, i, length, c);
  *   // use c
  * }</pre>
  *
  * When it is safe to assume that text is well-formed UTF-16
  * (does not contain single, unpaired surrogates), then one can use
  * U16_..._UNSAFE macros.
  * These do not check for proper code unit sequences or truncated text and may
  * yield wrong results or even cause a crash if they are used with "malformed"
  * text.
  * In practice, U16_..._UNSAFE macros will produce slightly less code but
  * should not be faster because the processing is only different when a
  * surrogate code unit is detected, which will be rare.
  *
  * Similarly for UTF-8, there are "safe" macros without a suffix,
  * and U8_..._UNSAFE versions.
  * The performance differences are much larger here because UTF-8 provides so
  * many opportunities for malformed sequences.
  * The unsafe UTF-8 macros are entirely implemented inside the macro definitions
  * and are fast, while the safe UTF-8 macros call functions for some complicated cases.
  *
  * Unlike with UTF-16, malformed sequences cannot be expressed with distinct
  * code point values (0..U+10ffff). They are indicated with negative values instead.
  *
  * For more information see the ICU User Guide Strings chapter
  * (https://unicode-org.github.io/icu/userguide/strings).
  *
  * <em>Usage:</em>
  * ICU coding guidelines for if() statements should be followed when using these macros.
  * Compound statements (curly braces {}) must be used  for if-else-while... 
  * bodies and all macro statements should be terminated with semicolon.
  *
  * @stable ICU 2.4
  */
 
 #ifndef __UTF_H__
 #define __UTF_H__
 
 #include "unicode/umachine.h"
 /* include the utfXX.h after the following definitions */
 
 /* single-code point definitions -------------------------------------------- */
 
 /**
  * Is this code point a Unicode noncharacter?
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 2.4
  */
 #define U_IS_UNICODE_NONCHAR(c) \
     ((c)>=0xfdd0 && \
      ((c)<=0xfdef || ((c)&0xfffe)==0xfffe) && (c)<=0x10ffff)
 
 /**
  * Is c a Unicode code point value (0..U+10ffff)
  * that can be assigned a character?
  *
  * Code points that are not characters include:
  * - single surrogate code points (U+d800..U+dfff, 2048 code points)
  * - the last two code points on each plane (U+__fffe and U+__ffff, 34 code points)
  * - U+fdd0..U+fdef (new with Unicode 3.1, 32 code points)
  * - the highest Unicode code point value is U+10ffff
  *
  * This means that all code points below U+d800 are character code points,
  * and that boundary is tested first for performance.
  *
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 2.4
  */
 #define U_IS_UNICODE_CHAR(c) \
     ((uint32_t)(c)<0xd800 || \
         (0xdfff<(c) && (c)<=0x10ffff && !U_IS_UNICODE_NONCHAR(c)))
 
 /**
  * Is this code point a BMP code point (U+0000..U+ffff)?
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 2.8
  */
 #define U_IS_BMP(c) ((uint32_t)(c)<=0xffff)
 
 /**
  * Is this code point a supplementary code point (U+10000..U+10ffff)?
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 2.8
  */
 #define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x10000)<=0xfffff)
  
 /**
  * Is this code point a lead surrogate (U+d800..U+dbff)?
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 2.4
  */
 #define U_IS_LEAD(c) (((c)&0xfffffc00)==0xd800)
 
 /**
  * Is this code point a trail surrogate (U+dc00..U+dfff)?
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 2.4
  */
 #define U_IS_TRAIL(c) (((c)&0xfffffc00)==0xdc00)
 
 /**
  * Is this code point a surrogate (U+d800..U+dfff)?
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 2.4
  */
 #define U_IS_SURROGATE(c) (((c)&0xfffff800)==0xd800)
 
 /**
  * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
  * is it a lead surrogate?
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 2.4
  */
 #define U_IS_SURROGATE_LEAD(c) (((c)&0x400)==0)
 
 /**
  * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
  * is it a trail surrogate?
  * @param c 32-bit code point
  * @return true or false
  * @stable ICU 4.2
  */
 #define U_IS_SURROGATE_TRAIL(c) (((c)&0x400)!=0)
 
 /* include the utfXX.h ------------------------------------------------------ */
 
 #if !U_NO_DEFAULT_INCLUDE_UTF_HEADERS
 
 #include "unicode/utf8.h"
 #include "unicode/utf16.h"
 
 /* utf_old.h contains deprecated, pre-ICU 2.4 definitions */
 #include "unicode/utf_old.h"
 
 #endif  /* !U_NO_DEFAULT_INCLUDE_UTF_HEADERS */
 
 #endif  /* __UTF_H__ */

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